Latex modified portland cement and use thereof in polymerization reactors

Abstract

In the aqueous polymerization of vinyl chloride and vinylidene chloride polymers and copolymers, the polymer build up normally experienced in many areas of commercial polymerization reactors is reduced, or when such polymer build up does occur it is more readily removed, when these trouble areas in polymerization reactors are coated with a latex-modified portland cement composition, the polymer in said latex containing carboxyl groups and the polymer having a Tg ° C. of less than about 40° C., preferably less than about 25° C.

I claim: 
     
       1. In the aqueous polymerization of vinyl halide monomers having the structural formula ##STR13## 
     
     
       where X is chlorine and Y is chlorine or hydrogen, in a polymerization vessel wherein there are areas of excessive polymer build up on the surfaces and fixtures in said vessel exposed to the suspension during said polymerization, the improvement comprising coating said areas of excessive polymer build up prior to the polymerization reaction with a composition comprising portland cement and an aqueous dispersion containing up to about 65 weight percent of a polymer containing about 0.1 to 25 weight percent carboxyl groups and having a Tg° C. of less than 40° C., said polymer present in said composition in an amount less than about 10 weight parts per 100 weight parts of said composition. 
     
     
       2. The polymerization of claim 1 wherein the portland cement is type I, II, or III containing about 40 to about 55 weight percent tricalcium silicate, the polymer contains about 1 to 10 weight percent carboxyl groups and has a Tg° C. of less than 25° C. 
     
     
       3. The polymerization of claim 2 wherein the cement is a type III cement and also contains 0 to 100 weight parts of a high alumina cement containing about 40 weight percent aluminum oxide, 0 to 100 weight parts of lime, and from about 100 to 600 weight parts of sand, per 100 weight parts of type III cement and the copolymer is a film-forming copolymer which contains butadiene, isoprene or a lower alkyl acrylate and about 1 to 10 weight percent of an α,β-olefinically unsaturated carboxylic acid containing 3 to 6 carbon atoms. 
     
     
       4. A suspension polymerization of claim 3 wherein the vinyl halide is vinyl chloride, said polymer contains an alkyl acrylate wherein the alkyl group contains 1 to 8 carbon atoms and about 1 to 10 weight percent acrylic or methacrylic acid, there being present in said composition from 4 to 8 weight parts of polymer per 100 weight parts of composition. 
     
     
       5. The polymerization of claim 3 wherein said composition contains hydrated lime and sand and said polymer is present in said composition in about 4.5 to 7.5 weight parts per 100 weight parts of cement, lime and sand. 
     
     
       6. The polymerization of claim 5 wherein said polymer contains an alkyl acrylate wherein the alkyl group contains 2 to 4 carbon atoms, about 2 to 8 weight parts acrylic or methacrylic acid and said latex contains less than one part per 100 weight parts of monomer of an emulsifier, suspension or dispersion agent and the catalyst is a persulfate catalyst. 
     
     
       7. The polymerization of claim 6 wherein said polymer is a copolymer of more than 40 weight parts butyl acrylate contains at least one of styrene and acrylonitrile and 1 to 10 weight parts of an acrylamide. 
     
     
       8. The polymerization of claim 7 wherein said cement composition contains an inhibitor selected from the group consisting of polar organic compounds and dyes. 
     
     
       9. The polymerization of claim 4 wherein said polymer contains at least one additional vinylidene monomer having at least one terminal CH 2  C<group 
     
     
       10. In the polymerization of claim 1, after the reactor is coated with the cement composition and prior to said polymerization, the exposed inner surface of said vessel and other means contained therein are coated with a polar organic compound or dye. 
     
     
       11. The polymerization of claim 10 wherein the inner surfaces of said vessels and other means are coated with a polyaromatic amine having a molecular weight in the range of about 250 to 2000 and having a softening point from about 65° to 175° C. 
     
     
       12. The polymerization of claim 11 wherein the polyaromatic amine is a reaction product of o- or m-phenylene diamine and resorcinol or bisphenol A, and alkali metal salts thereof.